It did go on for a bit too long; twenty minutes from the radiation booth to actual regeneration was too much in my opinion. I can understand not feeling so good about regeneration, Four did it well, but with Ten it came off as self-pitying. I can understand wanting to look back on the companions of that Doctor's era, Four, Five and Eleven did this well, but taking a whole ten minutes to have these huge farewells to characters we only saw a few episodes ago was just too much.
This leads to one of my biggest problems; there is no real sense of closure for the Tenth Doctor. Ten's character arc was about loss and sorrow, but in the end in just constantly loops back in on itself. Those feelings don't destroy him in the end, like Eight, but he doesn't get past them either, he just turns into Eleven, which basically turns into a hard reset for the series. He just ends up wallowing in self-pity, he neither gets worse or better and that always rubbed me the wrong way, it always made me think that RTD was basically saying "you can stop watching Doctor Who now, the only good Doctor is gone now."
I would have liked it if he learned to accept what had happened to him. I always thought that instead of going on about how he "could do so much more", if he ended up laughing bitterly at the irony of the situation; despite everything with the Master, Rassilon and the Time War, it all comes down to saving the life of an old man. He accepts it in the end of course, because if he can save the whole universe why not one more life? He's the Doctor, and the Doctor does what he can for his friends. Just wish it hadn't been radiation poisoning, already done that, might end up the laughing stock of the universe if it gets out he was killed by radiation twice.
The companion segment would be much shorter with the Doctor only thinking about his companions, an his last moments would be him learning that you can't let the awful things of your past hold you down, and that sometimes you need to just let go.
...I'm honestly disappointed that Ten never did learn that lesson.